So the coffee dyeing went fairly well. Definitively a way to destroy coffee. I also found my two value packs of british black tea I had bought just for dyeing a while ago. I am also no big fan of black tea, because it makes me feel quite weird. But the smell is very pleasant - I was just concerned that the vapours of so much tea would cause some insomnia but it seemed to have no effect whatsoever.
I found a recipe which said something like 8 tea bags for 5l, which would dye 100 g of yarn and I was surprised, checked my tea pack and realized I could have dyed 1kg of yarn with those 80 tea bags which were in it. I re-checked the reicpe and it said it would become some kind of beige, so I decided to make some experiments on my own.
First I used 10 bags, and that gave some quite dark beige, bright brown. Then I used the same dyebath again, put in new fiber and another 20 bags and reached a nice caramel brown. In the end, it put in the rest of the 50 bags and put in more silk and wool/silk blend and got some dark copper.
I like the colors, and it is really easy peasy with the tea bags, no filtering neccessary and no dirty fibers (as long as no tea bags burst open). And very nice colors for a low price.